27. Concatenation of Consecutive Binary Numbers

class Solution {
    public int concatenatedBinary(int n) {
        long res = 0;
        int mod = 1_000_000_007;
        for(int i = 1; i<=n; i++){
            String binaryString = Integer.toBinaryString(i);
            res = (res<<binaryString.length())%mod;
            res = (res+i)%mod;
        }
        return (int)res;
    }
}

class Solution {
    public int concatenatedBinary(int n) {
        long res = 0;
        int mod = 1_000_000_007;
        int size=0;
        for(int i = 1; i<=n; i++){
            if((i&(i-1))==0) size++;
            res = (res<<size | i) %mod;
        }
        return (int)res;
    }
}